1. Field of the Invention
The present invention relates, in general, to tape drives utilizing thin film magnetic heads for reading and writing data to magnetic storage medium (e.g., tape in cartridges), and, more particularly, to tape drives with magnetic heads that are useful for reading from and writing to tape using a new or present technology and its protocols while also being able to read legacy tapes that were written to with a prior or legacy technology and its protocols.
2. Relevant Background
In today's society, the need for storage of data in a secure and retrievable manner has continued to grow and likely will become even more important. There is a need not only to store data such as financial, health, and other information inexpensively but also such that it can be retrieved or read months or years from now such as to allow a company to recover from a loss of data caused by a natural disaster or technical failure. To this end, the data storage industry often stores data on disk or optical media for short term data storage and to magnetic tape or tape cartridges for long term storage or archive. Due to legal and other data retention requirements, it is desirable for the data or information on the tape cartridges to be accessible or readable for years (e.g., such as seven or more years). Each company or enterprise may use large numbers of tape cartridges to store their data, and as a result, some companies' largest expense associated with data backup and archiving is the storage media itself and not the tape drives and equipment used to access the tape cartridges.
An ongoing problem in the data storage industry is how to provide advances in data storage technology such as tape drive technology while allowing data storage customers to continue to use their existing libraries of tape cartridges. For example, magnetic read/write heads are used to read data from tape and to write data to tape. There is continued pressure to increase the amount of data that can be written to the same amount of tape, e.g., a demand to increase data density on a tape cartridge. One approach to achieve this goal is to reduce the width of the write elements used to write data and more tightly place write elements on the head. The read elements then are also reduced in size to read the narrower tracks of data on the tape surfaces. Unfortunately, these new and narrower read elements often cannot effectively read data written by older or “legacy” heads (or legacy tape drives). A further complication is that code and circuitry that is used to write and to read the data from the tapes, e.g., the recording and read channels, are also changing rapidly. Hence, a new and improved tape drive may include a new read channel that is matched with the drive's recording channel, but this may result in the new tape drive being unable to read data written with a predecessor or legacy tape drive that included a predecessor or legacy recording channel. In other words, each generation of tape drive may utilize differing recording and/or read channels to store data to and retrieve data from tape, and these channels often are not wholly compatible.
This problem may be considered or labeled a lack of backward read capability or legacy read capability that is needed to support media reuse. Media reuse is important as it protects a user's investments in media and automation infrastructure (e.g., tape library systems and equipment for particular tape cartridges). Reuse is the “reclaiming” of tapes or other media that may have been written by a legacy drive or a more advanced drive, and these reclaimed tapes are rewritten by a different drive that may be advanced, or not, relative to the original drive. Backward read capability also improves data migration efficiency and helps reduce the cost of converting media to higher capacity formats of the latest generation tape drives. Unfortunately, backward read capability has proven difficult to provide as customers have tape in their libraries that was written by the prior generation of tape drive and head technology as well as tape that was written by drives belong to much earlier generations (e.g., it is not really uncommon for a single customer to have cartridges from four or more generations of tape drives). Testing has indicated that using newer, typically narrower read elements with prewritten tapes provides typically poor to bad results based on detected data error rates, and the effectiveness of the newer heads generally decreases over time as wear occurs such as due to pole tip recession. Backward read capabilities of new drives are also reduced in some cases when a read channel is configured for a particular tape surface, e.g., burnished or smoother surfaces versus rough media. Presently, the solution has typically involved maintaining legacy drives for use with legacy tapes (or for recovery operations if the legacy tapes need to be used) and/or a costly and time consuming migration of data from the legacy tapes to new media, with the legacy tapes being eventually discarded.
There remains a need for a tape drive that provides enhanced backward read capability. Preferably such a tape drive would support media reuse by reading tapes or tape cartridges that were written by previously marketed product line of tape drives. It is also desirable for such tape drives to include the next step in technology so that the tape drives are also able to read/write at higher tape capacities or provide other read/write capabilities.